Lights are typically placed in enclosures called luminaires to redirect and diffuse the light that is emitted. Light fixtures commonly have a fixture body and a light socket to hold the lamp and allow for its replacement. Technically the lamp is the light source, typically called the light bulb. Fixtures may also have a switch to control the light. Fixtures require an electrical connection to a power source; permanent lighting may be directly wired, and moveable lamps have a plug. Light fixtures may also have other features, such as reflectors for directing the light, an aperture (with or without a lens), an outer shell or housing for lamp alignment and protection, and an electrical ballast or power supply.
The following functions are performed by the luminaire; (1) connection of lamp electricity supply to lamp; (2) contain control circuitry for lamp; (3) heat dissipation from the lamp; (4) reflection and redirection of light to a target area; (5) protection of the lamp from the environment (e.g. outdoors); (6) provide a decorative appearance; and (7) light distribution of the lamp.
Most lighting fixtures emit heat as well as light that must be removed. Possible problems resulting from overheating include degradation of electronic components, degradation of materials used in construction, and fire. The lamp and luminaire form an integrated unit, and lamps that exceed the rating of the luminaire should not be used. Similarly, Also, the class of the lamps installed in the luminaire (e.g. compact fluorescent or incandescent) should not be changed unless the luminaire is rated for the new class type. Use of a non-rated class could lead to overheating of the luminaire.
Common sources of lighting today are by use of incandescent and fluorescent lamps (or bulbs). Incandescent lamps generate light by passing electric current through a resistive filament, thereby heating the filament to a very high temperature so that it glows and emits visible light over a broad range of wavelengths. Incandescent sources yield a “warm” yellow or white color quality depending on the filament operating temperature. Incandescent lamps emit 98% of the energy input as heat. A 100 W incandescent light bulb for 120 V operation emits about 1,180 lumens, for about 11.8 lumens/W; for 230 V bulbs the figures are 1340 lm and 13.4 lm/W, respectively. Incandescent lamps are relatively inexpensive to make. The typical lifespan of an AC incandescent lamp is 750 to 1,000 hours. They work well with dimmers. Most older light fixtures are designed for the size and shape of these traditional bulbs.
Fluorescent lamps work by passing electricity through mercury vapor, which in turn emits ultraviolet light. The ultraviolet light is then absorbed by a phosphor coating inside the lamp, causing it to glow, or fluoresce. Conventional linear fluorescent lamps have life spans around 6,000 to 30,000 hours. The life expectancy depends on the number of on/off cycles, and is lower if the light is cycled often. The ballast-lamp combined system efficacy for then current linear fluorescent systems in 1998 ranged from 80 to 90 lm/W. For comparison, general household LED bulbs available in 2011 emit 64 lumens/W, with the best LED bulbs coming in at about 140 lumens/W. Because fluorescent bulbs contain toxic mercury, they are potentially hazardous and difficult to dispose.
Lighting can also be provided by light-emitting diodes, or LEDs. LEDs can be integrated into a variety of products, such as flashlights, light bulbs, and integrated light fixtures. LEDs are part of a family of lighting technologies called Solid-State lighting.
LED lighting products produce light very efficiently. LEDs are small light sources that become illuminated by the movement of electrons. LED lighting starts with a tiny chip (commonly about one square millimeter) comprised of layers of semi-conducting material. LED packages may contain just one chip or multiple chips, mounted on heat-conducting material called a heat sink and usually enclosed in a primary lens. The resulting device, typically several to a side, can be used separately or in arrays.
LEDs are highly directional light sources, whereas an incandescent or fluorescent bulb emits light—and heat—in all directions, resulting in significant energy losses. For direct lighting applications LED lighting uses both light and energy more efficiently despite higher initial costs.
The ability to use an LED to direct light allows for illumination of a flat defined target area requiring a lower luminous output compared to more traditional light sources, such as fluorescent or incandescent which would need reflectors or lenses to do the same. In comparison, the benefits of LED lighting are much smaller for illuminating a 360° orbit.
Like traditional light sources, the LED produces heat. Ultimately only about 30-40% of the input energy is turned into light, with the remaining 60-70% of the energy converted to thermal energy mainly by the way of non-radiative and combinative generated lattice vibration. Operating an LED at high temperatures lowers its efficiency and also the usable life of the LED. Thermal management is a key issue for LED products so reduction of heat generation improves luminous efficacy of LED.
LEDs are commonly thermally connected to a heat sink. For best performance this heat sink is thermally contiguous with the body of the luminaire and provides not only conductive cooling to the LEDs, but also provides convective cooling due to air circulation around the heat sink or luminaire body. Passive heat sinks are typically metal or other thermally conductive material attached to a component from which heat is transferred to the heat sink. The heat then radiates from the heat sink into the surrounding air. In many cases, passive heat sinks provide sufficient cooling. However, for heat sinks to be effective, particularly in high heat environments and/or high power applications, they should have large amounts of surface area from which to radiate the heat. The more surface area, the more heat that can be transferred to the surrounding air. Accordingly, some heat sinks have numerous fins, bends, or folds to increase surface area.
LEDs are diodes, which are electronic devices that allow current flow in one direction and block current flow in the reverse direction. LEDs thus have 2 electrodes, one positive (the cathode) and one negative (the anode). LEDs must be wired with the proper polarity or they will not illuminate, or could be damaged or destroyed. LEDs have some intrinsic resistance limiting current flow through them. Incandescent lamp filaments for example have a positive temperature coefficient of resistance; when they get hotter, their resistance rises. LEDs have negative temperature coefficient and the possibility of a thermal runaway. Proper heat sinking therefore is an important consideration for an LED.
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. A PCB populated with electronic components is called a printed circuit assembly (PCA), printed circuit board assembly. In informal use the term “PCB” is used both for bare and assembled boards. After the PCB is completed, electronic components must be attached to form a functional PCA.
Modular lighting systems offer a number of advantages in that the components simply plug together, making installation quick and easy, and yielding time and labor savings. The flexibility of modular lighting systems allows lighting fixtures to be easily relocated by unplugging connections, moving the fixtures, and plugging the cables back in again. The downside to modular lighting systems is principally cost. Individual modules invariably introduce extra materials such as plastic or metal module housings, and complex electrical and mechanical connectors. Moreover the cost of separately assembling the modules is an extra cost. A module may also restrict design elements in a luminaire and therefore aesthetics.
U.S. Pat. No. 5,672,000 to Lin titled Decorative Lamp Strip discloses, “[a]n improved decorative lamp strip comprising a three-strand flat electric wire, some main sets, some fixing plates, some sets of series connected conductive piece, some sets of a first parallel connected conductive piece, some sets of a second parallel connected conductive piece, some lamp seats and some bulbs with tungsten filament in general or some LED bulbs, wherein the flat electric wire comprises a middle strand series connected conductor and an upper and a lower strand parallel connected conductors, a plurality of holes are punched on the electric wire body, and each punched hole breaks the middle strand conductor, each main seat is installed in the position of each punched hole on the flat electric wire to engage with a fixing plate, and to let any one set of conductive piece installed on the main seat thrust into the middle, upper or lower strand conductor of the flat electric wire so as to combine a decorative lamp strip.”
U.S. Pat. No. 6,154,362 to Takashi et al. titled Display Apparatus discloses, “[a] display apparatus provided with display cells wherein LEDs are arranged in dot-like array within a case and molded by a mold portion within the case, and a unit portion accommodating therein a cell substrate on which the display cells are mounted. Further, there are provided ventilation holes formed so as to penetrate the display cells at prescribed positions in a direction from rear to front, a fan which is provided in an upper part of a rear surface of the unit portion can send cooling air into the unit portion and an opening portion formed at a bottom surface of the unit portion, thereby making it possible to discharge the cooling air sent by the fan to outside from the ventilation holes through the opening portion. Further, a penthouse unit is provided in front of the display cells and the cooling air discharged from the ventilation holes is caused to be returned to a side of the LEDs.”
U.S. Pat. No. 7,355,562 to Schubert et al. titled Electronic Interlocking Graphics Panel Formed of Modular Interconnecting Parts discloses a modular display panel is formed of a segmented symmetrical graphics panel having display pixels. The panel's interlock in for directions allows forming larger electronic graphics panel. The preferred shape of the panel is square, defining a perimeter with for edge surfaces. Each of those edge surfaces includes an electrical connection thereon. A frame assembly forms the outer portion of the panel, thereby allowing providing of signals and power to the units.” Further, the patent discloses “a new kind of electronic graphics panel formed of interlocking modules which can be interlocked together in order to form a graphics panel of any desired size. One aspect describes a light emitting diode (‘LED’) based modular graphics panel formed of interlocking modules that can be connected into any of a number of different arrangements. A computer may be used to control the display on the graphics panel. In an embodiment, the graphics panel is framed by a frame assembly which may include electronics therein, the electronics may include a memory that stores information to form a static display for an electronic sign or other application. Another feature of this system is the way that the modular blocks inter-connect which prevents upside down connection of the different modular blocks.”
U.S. Pat. No. 7,897,980 to Yuan et al. titled Expandable LED Array Interconnect discloses a “light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A light emitting device can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.”
U.S. Pat. No. 7,963,669 to Hockel et al. titled Modular Lighting System and Lighting Arrangement discloses “[a] modular lighting system having a plurality of light modules, which each have a plurality of light modules accommodating at least one light-emitting diode module. The light modules have at least two mounting clearances, which run substantially parallel, and a mounting rod passes through each mounting clearance for mechanical fixing and electrical contact-making purposes. The mounting clearances are formed on the luminaire body. A lighting arrangement of such lighting systems is also disclosed.”
U.S. Pat. No. 8,168,894 to Kuo titled Light Emitting Diode (LED) Circuit Board with Multi-Directional Electrical Connection discloses a “light emitting diode (LED) circuit board with a multi-directional electrical connection. The board includes a board body with a surface and an assembly plane as well as four sides and corresponding corners, and a plurality of positive and negative electric contacts, separately arranged onto the surface of the board body nearby four sides, and also arranged at intervals.” Additionally, “the LED circuit board with multi-directional electrical connection allows the board body to be provided with positive and negative electric contacts. It is possible to simplify the circuit of the LED circuit board of the present invention, helping to facilitate multi-directional electrical connection and expansion, and improve significantly the paving efficiency of LED circuit board with better practicability and industrial benefits.: Further, “[b]ased upon the branching sign, the installers may find it easier to identify if the positive and negative electric contacts at various sides of the board body are power input or output side, and then decide the arrangement direction of the board body. Based upon the structure of a notched flange preset at two connected sides of the board body of the LED circuit board, it is easy to break off the sides and level the fracture surface.”